libgap: what data in the libgap-calling functions must be declared volatile? other pitfalls?

[dimpase]

My libgap-calling code manages to cause infinite recursion in PRINT_OR_APPEND_TO_STREAM: it cannot open stream, tries to ErrorQuit few lines later, ErrorQuit in turns call PRINT_OR_APPEND_TO_STREAM, again it cannot open the stream, etc etc.

The (long) code causing this is here - I probably can produce a reasonably short C code illustrating this (by design, it does call libgap with quite a few invalid inputs, causing errors and processing them in a callback), but I'd rather try to fix things first...

While this potential infinite recursion in itself is a sort of bug in (lib)gap, could it be that my code violates some unwritten rules, e.g. does not use volatile for some data that needs it? Other pitfalls of this sort?

Would it matter if the caller is multi-threaded (which is the case for me) and calls libgap in different threads?

[fingolfin]

If you call GAP from multithreaded code, then you as caller must take care that no two such calls can run simultaneoulsy, e.g. via a lock, else all hell will break loose.

[fingolfin]

The issue you describe at the start sounds like a duplicate of #3028 which should be fixed in GAP 4.11. There are no other API considerations to mention, but keep in mind that GAP is strictly single threaded, and hence so is libgap. Callers have to take care to call it from at most one thread at a time (or possibly even restrict all calls to it to a single thread).